High data rate signal transmission is a concern in many systems. Current server systems, for example, often use a set of rack mounted components or user-selected blades that work together to provide data storage, processing, and communications, and the individual components often need to communicate with each other at high data rates to provide the desired system performance. In a server system using blades, the blades, e.g., server blades and storage blades, are mounted in a common enclosure and share components such as cooling fans, power supplies, and enclosure management. In general, data signals transmitted among the blades must collectively provide high data rate transmissions. With current technology, each data signal may have a bandwidth of about 10 Gbit/s or more, and several parallel data signals may be required to provide the desired data flow rate.
Electrical signals generally oscillate at high frequencies to provide high data transmission rates, and the high frequency oscillations can present impedance and noise problems for electrical signals transmitted over copper wires or traces. Optical signaling can avoid many of these problems, but optical signaling may still require complex waveguide systems for dealing with loose optical cables or ribbons that must be connected or disconnected when components are installed or removed. Free-space optical signaling avoids the use of complex systems of optical fibers or waveguides but must address alignment issues. In particular, optical signaling generally requires circuits for conversion between optical and electrical signals, and a receiver converting a high data rate optical signal to an electrical signal for an electronic component generally requires a small-area, low-capacitance photodiode because of the high frequency of the electrical signal. Directing a free-space optical signal onto the small area of the photodiode generally requires use of precise alignment systems that in many applications must be able to adjust or adapt to relative system movements or vibrations. Methods and systems for transmitting high data rate signals that avoid the problems associated with wires and optical fibers or waveguides and that simplify component alignment are sought.